1. Field of the Invention
The present invention relates to a fixing heater for fixing a toner image on a recording material, as well as a fixing device employing the same.
2. Description of the Related Art
The heat roller fixing method has been widely adopted for fixing a toner image on a recording medium.
It has also been proposed to fuse a toner through a web, as is disclosed in the specification of U.S. Pat. No. 3,578,797.
However, the above-described fixing methods employ a heating roller whose heat capacity is very large, and this makes the warming up time required for the roller long and necessitates application of high power.
In order to solve this problem, the present inventors have filed application Ser. No. 206.767, and proposed a fixing device whose heat capacity is small, which requires low power, and whose warming up time is short.
Furthermore, in the above-described types of heat fixing devices, a temperature fuse or a thermostatic switch is provided as a safety measure on the surface of a heat roller so as to forcibly de-energize the heater when the temperature thereof rises excessively.
When such safety measures as a temperature fuse or a thermostatic switch are applied to the fixing heater having a wire-like heat generating layer whose heat capacity is small, the response is delayed because they cannot be disposed in the heat generating portion. Furthermore, the warming up time is prolonged due to the large thermal capacity of the temperature fuse or of the thermostatic switch.